[Amps] SWR and amplifiers

[Gary Schafer]

Jim Garland has it right.

Disregarding any line loss:
Your amp is putting out 900 watts. The wattmeter shows 1000 watts because
the reflected 100 watts is re-reflected back towards the antenna and adds to
the 900 watts from the amp on the wattmeter. The wattmeter shows 1000 watts
(assuming the wattmeter is a meter such as a Bird).

The Bird manual tells you to subtract the reflected reading from the forward
reading to obtain the true power delivered to the line/antenna.

Most of the electronic watt meters such as the LP 100 calculate this for you
so the forward power reading already has the reflected power subtracted for
you. It would read 900 watts forward.
But I think you already knew all of this.

73
Gary  K4FMX


> -----Original Message-----
> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Bill Turner
> Sent: Wednesday, May 24, 2017 9:45 PM
> To: qrv at kd4e.com; Amps group
> Subject: Re: [Amps] SWR and amplifiers
> 
> I think here's what's happening:  The meter shows 1000 watts of
> forward power and that is really true - the amplifier really is
> putting out 1000 watts. The 100 watts of reflected power is
> re-reflected back to the antenna where 90% of it is radiated and the
> rest is re-re-reflected back to the transmitter and then
> re-re-re-reflected again back to the antenna. This bouncing back and
> forth keeps up until it is essentially gone or dissipated in the feed
> line.
> 
> So, is the figure of 100 watts reflected actually the sum of the
> original reflection plus all the re-reflections? Seems like it would
> be.
> 
> 73, Bill W6WRT
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